Mitigation of PFSA membrane chemical degradation using composite cerium oxide–PFSA nanofibres
A PFSA nanofibre-network enriched with cerium oxide nanoparticles (NFCeOx) has been developed as a trap for highly reactive oxygen species that are produced in an operating fuel cell and that lead to membrane degradation and failure. This new mitigation strategy allows the location of CeOx at the membrane electrode interface. The composite nanofibre web was deposited by electrospinning of dispersed Nafion® and CeOx nanoparticles, using a polyethylene oxide carrier polymer. Asymmetric composite Nafion® membranes were prepared by bonding the nanofibre web to one side of the membrane. In accelerated stress testing by OCV hold testing, a membrane electrode assembly with the modified membrane surface oriented to the anode gave a very stable open circuit voltage and a lifetime close to 1000 hours, while the end of life occurred at close to 100 hours for unmodified Nafion® 212. The results of characterisation by X-ray photoelectron spectroscopy, Raman spectroscopy and scanning electron microscopy of end-of-life MEAs and analysis of fuel cell effluents were used to explain the degradation processes occurring within the modified and unmodified membranes.